A connection device which is used to connect two objects or to connect two ends of one object, is widely used in all kinds of products. According to the different requirement of different kinds of products, connection devices are configured with different structures or connection methods. For example, a connection device for connecting two ends of a necklace includes a closed ring and a movable retaining ring. By opening the movable retaining ring to connect it with the closed ring, the two ends of the necklace can be connected to wear. By opening the movable retaining ring to separate it from the closed ring, the two ends of the necklace are disconnected for facilitating to store. This kind of connection device has a comparatively simplistic structure and so is inconvenient to use. Furthermore, this kind of connection device is easily deformed after being used for many times, which adversely affects the connection performance.
However, with the improvement of living standards of people, the requirement to a connection device is gradually increased. The connection device is not only required to meet the requirement of general function, but also required to be more convenient, firmer, more durable and more funny to use and to be suitable for more people in different environments. So, the conventional connection device is required to be improved or it is required to provide some new connection devices.